Measuring device

ABSTRACT

In order to check and measure the skewness of crashed cars before as well as during and after repair it is known to use rulers provided with perpendicularly extending mandrels in both ends, and it is also known to use a ruler that is provided with a magnetic fastening means in one end. These devices are simple and easy to use and provide a surprisingly great precision in work. In reality however one must write down taken measures of remember them between measurements. Furthermore the precision is dependent of the skill or practice of the user of the device since an inclining of the device may change the result, also that the skill at reading a scale and the reading conditions exert a strong influence.

[0001] In order to check and measure the skewness or distortion ofcrashed cars before as well as during and after repair it is known touse telescopically extendable measuring devices or rulers provided withperpendicularly upwards extending mandrels in both ends. It is alsoknown to use a ruler that is provided with a magnetic fastening bracketin one end (SE 9704438-2). These devices are simple, easy to handle andresult in a surprisingly high precision in the work. In reality onehowever has to write down taken measures or alternatively remember themeasures between the measurements. Furthermore the precision isdependent of the skill or practice of the one using the device since aninclining of the ruler may change the result. Likewise the skill andconditions when reading scales are of essential influence.

[0002] The object of the invention is to eliminate as much as possiblethe above problems without impairing the simplicity and speed in thehandling, but preferably to improve it further.

[0003] In accordance with the invention the above problem is solved witha telescopically extendable ruler provided with measurement mandrels orsuitable measurement bodies in the ends, the ruler being provided with adigital measuring means for the extension or length of the ruler. Theprevious scale is thus replaced with an electronic measuring andindication of the extended measure. In this way it is no longernecessary that the user is precisely at the correct place on the side ofthe measuring device in order to see the scale perpendicularly and alsofrom other aspects in the identical way each time. The risk that heshadows the scale that he is to read is also reduced and since thedevice can remember a measured value for the user it is ready to comparea later taken value even if it is several minutes between them. If sodesired one can consider, instead of measuring absolute values tomeasure differences that is a measure that has been taken on anundamaged part of the car is set to zero and can be compared with ameasure taken on a damaged side. This facilitates in particular themeasuring during straightening operations. It is also easier to remembersmall figures than larger ones.

[0004] An additional error source at this type of measuring rulers isthat the magnet fastener, that in itself allow a fast and simplehandling of one person even at long measures, if it is mounted with aslight error or at least in different ways on the left and right sidecan give different measures even if the measure are actually the same. Alittle dirt under the magnet gives an inclination of the fastener thatmay cause a miss-measuring. In order to eliminate this problem it isaccording to a further development of the invention suggested thatinstead of joining the ruler to the magnet the ruler is joined to themandrel while the magnet is moveable. By additionally arrange the rulermoveable in a universal joint arranged principally inside the cone thatcarry out the centering in relation to the hole the measuring will inreality take place from the center of the hole and there is no influencefrom the inclination of the magnet, that may be caused by a locallydented surrounding, dirt, underbody coating etc. The probability for theoccurring of such damages is far larger than for the hole to change itslocation in relation to the longitudinal or lateral direction of thecar.

[0005] Since the force that the centering mandrel or cone is subjectedto is exclusively directed towards the vehicle one can consider that thecentering tip or cone that is journaled on a ball is provided with sometype of snap lock so than one simply snaps on the conical tip on theuniversal joint. In this way one can use differently wide conesdepending on the size of the hole so that it is actually possible toplace the universal joint precisely in the center of the hole. One canalso contemplate the use of other types of points or tips,

[0006] In order further to simplify the invented device it is accordingto a further development of this suggested that the device is providedwith an adjustable spirit level on the side or on top of the ruler anddirected along the ruler. In this way it becomes possible to take ameasurement between two known and undamaged points in the longitudinaldirection of the car. The measuring mandrel in the outer end of theruler is adjusted to the height required to give an orientation of theruler parallel to the datum plane of the car. The spirit level is nowadjusted to an entirely level position. The spirit level together withits fastening bracket is then turned 180° and then the entire ruler isturned or moved so that its ends change place in relation to the vehiclethat is to be measured. The spirit level will now with the ruler placedlengthwise of the car represent a definition of the datum plane of thevehicle allowing quick and normalized measuring. A supposition for thisis that the vehicle stands comparatively even laterally but since thisnormally is the case it is no problem, it is however more common thatthe vehicle is inclined in its length direction.

[0007] The electronic digital measuring of the extension of the ruler ispreferably done by means of a device located in one of the telescopingtubes. The device comprise a thin metal tape that is fastened in theother end of the ruler. The tape runs over a rotatable drum. A springdevice is arranged to pretension the drum so that the tape always iskept stretched. The extended length is then detected by the drum orroller for the tape having a toothed or screen pattern provided wheelthat pass between a light source and a photo detector generating pulsesas the drum or wheel rotates and the pulses can then simply be countedand transformed to measures shown on a display in the end of the ruler,either in millimeters or in inches.

[0008] further advantages and characteristics of the invention areapparent from the following description of a preferred embodiment of theinvention with reference to the enclosed drawings. In these FIG. 1 showsa measuring ruler in accordance with the invention in a perspective viewand partly in section, FIG. 2 an exploded view of a magnet fasteningbracket, FIG. 3 the ruler in a perspective view and FIG. 4 an adjustablespirit level means.

[0009] The ruler shown in the drawing includes a number of in each othertelescoping tubes 1-4. The tube device is in the end with the outermostand largest tube provided with a magnetic fastening bracket 5, in theother end, the one with the thinnest of the tubes 4 a perpendicularmandrel or corresponding is arranged with a shaft 15 that can be lockedin a bracket 7.

[0010] The magnetic fastening includes a conical mandrel 8 thatinternally is snapped over a ball that in turn with a short essentiallycylindrical shaft 10 is detachably fastened to an end piece 11 in theouter end of the ruler. On the cone a circular magnet 12 is displaceableaxially and fastened in a casing 14 holding a pressure spring. Thecasing is by the spring biased away from the cone 8 and the ball 9towards the ruler itself. The spring is however sufficiently weak inrelation to the force exertable by the magnet when after the placing ofthe cone in the intended measuring hole the magnet is then moved againstthe force of the spring into contact with the metal around the hole andthe resulting attraction force of the magnet push via the ball and thespring the cone against the hole. By choosing cone according to holediameter by simply snapping off and on different cones the universaljoint can be located with its center of movement in level with the holein itself and the ruler will thus measure distances precisely to thecenter of the hole.

[0011] In the other end of the ruler a digital display is arrangedintegrated with the bracket 7 for the mandrel 6. The digital displayalso include a number of control buttons. The display can either bebrought to indicate the measured distance between the center of theuniversal joint in the other end and the tip of the mandrel in the otherend of the ruler, alternatively the digital device may be adjusted sothat it shows 0 for a first such measure and then only show differencesrelative this value so that users directly get a measure of how much ameasuring point has to be displaced and the vehicle be straightenedrespectively.

[0012] I order to deliver the measures of the length of the ruler to thedigital display there is inside the ruler a thin metal tape 16 thatextends from the other end (the one with the magnet fastening bracket 5)of the ruler to the inner end of the innermost tube 4 where a measuringunit 17 is fastened to the innermost tube. The tape 16 is in the unit 17wound on a small drum. On the same drum a band 18 is arranged with theopposite winding direction and extending in the opposite direction, thatis towards the bracket 7 to which the band is connected via a pullingspring 19. Since the part of the drum where the band with the spring 19is wound has a smaller diameter than where the measuring tape 16 iswound the required spring length necessary always to keep the metal tapestretched is reduced.

[0013] The drum is further provided with a radially extending rim ofsmall pins or teeth that at the rotation of the drum pass between alight source and a photosensitive element so that each tooth give apulse. These pulses can then be counted by the digital display deviceand be used as base measures for the measuring. At the calculation thenumber of pulses to for instance millimeters and also the changingdiameter with which the tape is wound on the drum is considered, thissince the diameter changes with the number of turns that have alreadybeen wound onto the drum.

[0014] Since the above described measuring unit will be very light itbecomes also in reality robust and need not to be damaged even if theruler as such is handled comparatively carelessly.

[0015] The measuring unit also constitute a guide for the innermost tubein the next smallest one. Also the two middle tubes are provided withguides 24 and 25 in the inner ends. The guides of the inner ends arealso provided with spring biased contact heels 26 to eliminate play.These contact heels also serv to prevent the tubes from being drawn outof each other. The tubes 1-3 also have outer guides 27-29 that also servas seals.

[0016] The measuring display provided tube 4 is preferably in the sameend provided with a spirit level 20, the inclination of which isadjustable in relation to the longitudinal direction of the ruler. Theadjustment of the inclination is carried out through the spirit levelbeing journaled in a bracket 21 in one end 22 and provided with anadjustment screw 23 in the other end. The bracket is furthermore able toswivel in the bracket 7 around an axle arranged vertically andperpendicular relative the length direction of the ruler. In this way itbecomes possible to adjust the spirit level so that it is horizontal byfirst applying the ruler to undamaged parts of the car and with amandrel length that locates the ruler in the datum plane of the car orparallel therewith. As soon as the spirit level is horizontal the ruleris parallel to the datum plane. In this way also height measurementswith great precision becomes possible. If it at the adjustment of thespirit level should be necessary or practical for the ruler to extend inthe opposite direction of the vehicle the spirit level bracket 21 ispivoted one half turn around the vertical pivot axle so that despite theturn about of the ruler the spirit level can indicate the datum plane.In this way the number of possible influencing angles and measures isconsiderably reduced and the precision of executed measurementsincrease. The spirit level may either as shown be located on top of theruler facing the vehicle that is to be measured, or alternatively thespirit level may be arranged on the side of the ruler but so that itstill can be swiveled 180° to enable the above operation.

[0017] The device described above is extremely easy to handle, sure andhas good precision and facilitates dramatically the work. The ruler maybe provided with different types of adaption pieces in both ends foradaption to the measurements and the objects on which measuring is totake place. Furthermore one can consider instead of measuring, to enterthe expected or prescribed value for a measurement first and then theruler is applied and the difference is taken and displayed.

[0018] Since electricity already is at hand in the ruler the spiritlevel can be made illuminable with a light emitting diode or the like.

1. Measuring device or ruler intended for symmetry measurements ofvehicles, characterized in that it is provided with built in measuringmeans for the extension of the ruler and transfer of these data orfigures to a display.
 2. Measuring ruler according to claim 1,characterized in that the measuring means is constituted by a tapeextending from one end of the ruler to the other end where the tape iswound on a drum spring biased in the winding direction, which drum isprovided with cogs or teeth and that the passage of these is detectedand counted by means of a light source and a photo diode and that thedrum rotation detected in this way is used to provide a measure of theextending of the ruler.
 3. Measuring ruler according to claim 2,characterized in that the spring bias is achieved by a band or threadwound on the same drum as the tape and fastened in a pull spring. 4.Measuring ruler according to claim 3, characterized in that the band orthread is wound onto a part of the drum that has a smaller diameter thanthe one where the tape is wound.
 5. Measuring ruler according to claim 2or 3, characterized in that the changing diameter of the tape when woundis taken into consideration before the measured values are presented onthe display.
 6. Ruler according to claim 1, characterized in that itincludes a spirit level arranged pivotable in one end and adjustable inthe other end, which spirit level entity in its entirety in turn is ableto swivel around a vertical axis between two relative each other 180°turned positions.
 7. Ruler according to claim 6, characterized in thatthe spirit level is arranged on the top of the ruler.
 8. Ruler accordingto claim 6, characterized in that the spirit level is arranged on theside of the ruler.
 9. Ruler according to claim 1, characterized in thatthe ruler in the end opposite to the display provided end is providedwith a magnetic fastening means including a conical part that isconnected to the ruler and that around the conical part a displaceablemagnet is arranged lightly spring biased away from the tip of theconical part, and that the magnetic force is greater than the springbias.
 10. Ruler according to claim 1, characterized in that the displayis arranged in one end of the ruler, in particular in the end with themeasure mandrel.
 11. Ruler according to claim 9, characterized in thatthe conical part is articulated on a ball essentially in level with forinstance a hole.